my flight reached guangzhou int. airport at 00.35 (midnight). how do i travel to jieyang.

I am afraid that you need to stay one night, because there is no bus or train to take you to reach Jieyang at that time.
It is suggested to take the airport shuttle bus line 6 to reach its terminal near the local East Railway Station. Then the next morning, you can take a taxi to reach the Tianhe Bus Terminal where you can find direct buses to reach Jieyang directly.